"It is clear the IRS cannot operate with even a shred of the American people's confidence under the current leadership," Rubio said in a letter to Treasury Secretary Jack Lew. "Therefore, I strongly urge that you and President Obama demand the IRS commissioner's resignation, effectively immediately. No government agency that has behaved in such a manner can possibly instill any faith and respect from the American public."

Rubio also called on Lew to ensure the Treasury Department’s full cooperation with any investigations regarding the scandal.

“The American people deserve answers about how such seemingly unconstitutional and potentially criminal behavior could occur, and who else was aware of it throughout the Administration,” Rubio wrote. “If investigations reveal that bureaucrats or political appointees engaged in unconstitutional or criminal targeting of conservative taxpayers, they must be prosecuted to the fullest extent of the law.”